The invention is based on the following state of the art:
The invention starts from a process such as may, for example, be performed using a gas processor as described in DE 33 12 863 C2. In that process the solid matter to be processed which contains gasifiable organic material, passes under the action of gravity through a pyrolysis chamber in which initially—in the absence of air—these solids are thermally subjected to dry distillation at a temperature of about 500° C. and are subsequently gasified for fuel gas generation by the addition of gasification medium at a temperature of about 800° C. The gasification media are introduced substoichiometrically in relation to the oxidisable material content. The organic solids which are fed into the upper region of the pyrolysis chamber form in the gas processor a particulate solids bed, which is supported by a material lock element which limits the pyrolysis chamber at its lower end. In the region of the material lock element passages are provided for the fuel gas generated in the pyrolysis chamber. The residual material as well, which remains after the conversion of the organic solids in the particulate solids bed, emerges through the passages downwardly from the pyrolysis chamber. The material lock element is movable and promotes, acting as a discharge element, the discharge of the residues from the particulate solid bed. The gasifying media, air and/or steam, which are introduced into the particulate solids bed in substoichiometrical ratio, pass through the particulate solids bed in the direction of gravity, something which is attained by the maintenance of a pressure gradient between the feed locality of the gasification media into the pyrolysis chamber and the outlet for the fuel gas at the passages associated with the discharge element. Accordingly, dry distillation volatiles and gasification media as well as the fuel gas generated in the pyrolysis chamber pass through the gas processor in co-current.
Using this flow mode, the dry distillation volatiles generated in the dry distillation zone of the particulate solids bed during dry distillation of the organic solids are passed through the gasification zone following downstream in the pyrolysis chamber such that part of the pyrolysis volatiles react with the gasification media and are combusted. In the region of the discharge element there is formed accordingly an embers bed. It is a feature of the gas processor known from DE 33 12 863 C2 that the dry distillation volatiles while passing through the embers bed are cracked: the tarry long-chain hydrocarbon components and other condensable compounds of the dry distillation volatiles are converted into non-condensable short-chain hydrocarbon and other low molecular weight compounds. A high-quality fuel gas is thus formed which can be utilised not only by being combusted and used as heating gas in heat exchangers for heat generation, but it can also be used as a fuel for the operation of internal combustion engines.
Dry distillation, also known as low temperature carbonisation, is a process, wherein carbonaceous solids, such as wood, but also waste materials such as old tyres and plastic wastes are heated to temperatures at which the solids are decomposed to release a variety of volatiles and to usually leave behind a carbonised residue such as coke or charcoal.
It is a problem in the process of the afore described type that inside the particulate solid bed, where lumps of varying sizes occur of the organic material to be processed, no homogeneous solids density can be attained as a result of which the reduced pressure in the combustion chamber below the discharge element for the withdrawal of the gases will not result in a constantly maintained pressure gradient within the particulate solids bed. In such regions within the particulate solids bed, in which material bridges and cavities are formed, faulty reactions and undesired flame breakthrough may occur, even in a direction opposite to the set up co-current direction. Likewise, an inadequate conversion of the dry distillation volatiles may occur in the embers bed whereby the quality of the fuel gases generated is compromised by dry distillation volatiles inadequately cracked in the embers bed being drawn off prematurely. Frequently the setting up of optimal parameters for the gasification process and for the conversion of dry distillation volatiles in the embers bed results in undesirable conditions in the particulate solids bed of the dry distillation zone and vice versa, such that the control of the gas processor is unstable.
The structure of the particulate solids bed and the dry distillation attained in the particulate solids bed, degassing and gasification are dependent on the solids to be converted, their properties and geometrical configurations, in particular their homogeneity and sizing. If an optimised gas generation is to be attained, the gas generator must in each situation be adapted to these material properties and geometrical configurations. For attaining a high fuel gas quality, the dimensions and the design of the gas generator are, therefore, also crucial. This applies particularly in the context of channelling in the particulate solids bed. Whether such particulate solids channelling has a negative effect also on the conversion of the solids and on the fuel gas quality attained in the gas processor will, however, also depend on the technical design and construction of the pyrolysis chamber. It is known to provide in the pyrolysis chamber agitation elements, which break up channelling formed in the particulate solids bed whenever they occur, in which context reference is made, for example, to DE 197 55 700 A1.
From DE 30 49 250 C2 it is known to convert the input material in two stages. The material is initially dried and devolatilised in a rotary drum and thereafter the fuel gas is generated in a gasification shaft reactor downstream of the rotary drum. In this context a separation of the solids may be performed where the devolatilised material exits from the rotary drum so that only part of the material, i.e. the material which has been carbonised in the rotary drum is introduced into the gasification shaft reactor. Components of the solid feed materials which are unsuitable for gasification, are separately discharged before they can enter the gasification shaft reactor. In order to dry and devolatilise the material, the exterior wall of the rotary drum is heated, drying and devolatilisation being performed in the absence of air. The gases thereby formed are withdrawn from the rotary drum in the conveyance direction of the material in co-current It is a disadvantage that the thermal conditions for the formation of dry distillation volatiles are not adequately adaptable dynamically to the conversion in the gasification shaft reactor. The required control of the processor reacts too slowly when adaptations are necessary to the material conversions taking place and, more particularly, the gas processor is adaptable to different qualities of available materials for processing only at high cost.
A need has been recognised to provide a process and a gas generator adaptable in a simple manner to whatever solids must be processed. On the one hand, the solids are to form within the gas generator a particulate solids bed which is optimised for the fuel generation and within which an adequate dry distillation of the material can be attained. On the other hand, the high molecular weight hydrocarbon and other compounds in the dry distillation volatiles should be cracked as completely as possible in the gas processor. Dry distillation and gasification should be adaptable to one another in an optimised manner depending on the material to be processed. For that purpose it has now been recognised in accordance with the invention that more effective and more reliable intimate contact needs to be achieved for an adequate duration within an appropriately set up temperature range to ensure adequate and substantially complete cracking of all condensable volatiles which otherwise interfere with the satisfactory operation of internal combustion engines and which can even interfere with the operation of sensitive burner nozzles.
It is, moreover, the intention that the gas generator, even after having been taken into operation, should be adaptable and dimensionable with relatively little effort in accordance with data which are established empirically only during actual operation.
Particular needs have been recognised for a fuel gas generator process and apparatus that is on the one hand readily adaptable on the spot to changing circumstances and is on the other hand fully self-sufficient and therefore suitable for being used as a decentralised power source, capable of being operated independently of whether or not a power grid is available.
These needs are even more pressing in remote and underdeveloped regions inter alia in the following respects and to fill the following needs:    ability to utilise all kinds of available combustible materials (gasifiable and/or dry-distillable);    seasonal variations of these supplies;    wastes which need to be disposed of;    energy needs: mechanical, electrical and thermal energy and fluctuations of these needs;    alternative uses of the products of dry distillation and/or gasification.